[llvm-commits] CVS: llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
Evan Cheng
evan.cheng at apple.com
Fri Feb 9 12:55:10 PST 2007
Changes in directory llvm/lib/Target/ARM:
ARMConstantIslandPass.cpp updated: 1.24 -> 1.25
---
Log message:
Add reference counting to constantpool entries. Delete the unused ones.
---
Diffs of the changes: (+113 -36)
ARMConstantIslandPass.cpp | 149 ++++++++++++++++++++++++++++++++++------------
1 files changed, 113 insertions(+), 36 deletions(-)
Index: llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
diff -u llvm/lib/Target/ARM/ARMConstantIslandPass.cpp:1.24 llvm/lib/Target/ARM/ARMConstantIslandPass.cpp:1.25
--- llvm/lib/Target/ARM/ARMConstantIslandPass.cpp:1.24 Fri Feb 2 20:08:34 2007
+++ llvm/lib/Target/ARM/ARMConstantIslandPass.cpp Fri Feb 9 14:54:44 2007
@@ -24,11 +24,12 @@
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
+#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
-#include <iostream>
using namespace llvm;
+STATISTIC(NumCPEs, "Number of constpool entries");
STATISTIC(NumSplit, "Number of uncond branches inserted");
STATISTIC(NumCBrFixed, "Number of cond branches fixed");
STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
@@ -51,13 +52,13 @@
/// BBSizes - The size of each MachineBasicBlock in bytes of code, indexed
/// by MBB Number.
- std::vector<unsigned> BBSizes;
+ SmallVector<unsigned, 8> BBSizes;
/// WaterList - A sorted list of basic blocks where islands could be placed
/// (i.e. blocks that don't fall through to the following block, due
/// to a return, unreachable, or unconditional branch).
- std::vector<MachineBasicBlock*> WaterList;
-
+ SmallVector<MachineBasicBlock*, 8> WaterList;
+
/// CPUser - One user of a constant pool, keeping the machine instruction
/// pointer, the constant pool being referenced, and the max displacement
/// allowed from the instruction to the CP.
@@ -71,7 +72,22 @@
/// CPUsers - Keep track of all of the machine instructions that use various
/// constant pools and their max displacement.
- std::vector<CPUser> CPUsers;
+ SmallVector<CPUser, 16> CPUsers;
+
+ /// CPEntry - One per constant pool entry, keeping the machine instruction
+ /// pointer, the constpool index, and the number of CPUser's which
+ /// reference this entry.
+ struct CPEntry {
+ MachineInstr *CPEMI;
+ unsigned CPI;
+ unsigned RefCount;
+ CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
+ : CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
+ };
+
+ /// CPEntries - Keep track of all of the constant pool entry machine
+ /// instructions. For each constpool index, it keeps a vector of entries.
+ std::vector<std::vector<CPEntry> > CPEntries;
/// ImmBranch - One per immediate branch, keeping the machine instruction
/// pointer, conditional or unconditional, the max displacement,
@@ -88,11 +104,11 @@
/// Branches - Keep track of all the immediate branch instructions.
///
- std::vector<ImmBranch> ImmBranches;
+ SmallVector<ImmBranch, 32> ImmBranches;
/// PushPopMIs - Keep track of all the Thumb push / pop instructions.
///
- std::vector<MachineInstr*> PushPopMIs;
+ SmallVector<MachineInstr*, 4> PushPopMIs;
/// HasFarJump - True if any far jump instruction has been emitted during
/// the branch fix up pass.
@@ -109,9 +125,10 @@
private:
void DoInitialPlacement(MachineFunction &Fn,
- std::vector<MachineInstr*> &CPEMIs);
+ SmallVector<MachineInstr*, 16> &CPEMIs);
+ CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
void InitialFunctionScan(MachineFunction &Fn,
- const std::vector<MachineInstr*> &CPEMIs);
+ const SmallVector<MachineInstr*, 16> &CPEMIs);
MachineBasicBlock *SplitBlockBeforeInstr(MachineInstr *MI);
void UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB);
bool HandleConstantPoolUser(MachineFunction &Fn, CPUser &U);
@@ -147,7 +164,7 @@
// Perform the initial placement of the constant pool entries. To start with,
// we put them all at the end of the function.
- std::vector<MachineInstr*> CPEMIs;
+ SmallVector<MachineInstr*, 16> CPEMIs;
if (!MCP.isEmpty())
DoInitialPlacement(Fn, CPEMIs);
@@ -182,7 +199,9 @@
BBSizes.clear();
WaterList.clear();
CPUsers.clear();
+ CPEntries.clear();
ImmBranches.clear();
+ PushPopMIs.clear();
return MadeChange;
}
@@ -190,7 +209,7 @@
/// DoInitialPlacement - Perform the initial placement of the constant pool
/// entries. To start with, we put them all at the end of the function.
void ARMConstantIslands::DoInitialPlacement(MachineFunction &Fn,
- std::vector<MachineInstr*> &CPEMIs){
+ SmallVector<MachineInstr*, 16> &CPEMIs){
// Create the basic block to hold the CPE's.
MachineBasicBlock *BB = new MachineBasicBlock();
Fn.getBasicBlockList().push_back(BB);
@@ -211,8 +230,13 @@
BuildMI(BB, TII->get(ARM::CONSTPOOL_ENTRY))
.addImm(i).addConstantPoolIndex(i).addImm(Size);
CPEMIs.push_back(CPEMI);
- DEBUG(std::cerr << "Moved CPI#" << i << " to end of function as #"
- << i << "\n");
+
+ // Add a new CPEntry, but no corresponding CPUser yet.
+ std::vector<CPEntry> CPEs;
+ CPEs.push_back(CPEntry(CPEMI, i));
+ CPEntries.push_back(CPEs);
+ NumCPEs++;
+ DOUT << "Moved CPI#" << i << " to end of function as #" << i << "\n";
}
}
@@ -233,11 +257,26 @@
return false;
}
+/// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
+/// look up the corresponding CPEntry.
+ARMConstantIslands::CPEntry
+*ARMConstantIslands::findConstPoolEntry(unsigned CPI,
+ const MachineInstr *CPEMI) {
+ std::vector<CPEntry> &CPEs = CPEntries[CPI];
+ // Number of entries per constpool index should be small, just do a
+ // linear search.
+ for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
+ if (CPEs[i].CPEMI == CPEMI)
+ return &CPEs[i];
+ }
+ return NULL;
+}
+
/// InitialFunctionScan - Do the initial scan of the function, building up
/// information about the sizes of each block, the location of all the water,
/// and finding all of the constant pool users.
void ARMConstantIslands::InitialFunctionScan(MachineFunction &Fn,
- const std::vector<MachineInstr*> &CPEMIs) {
+ const SmallVector<MachineInstr*, 16> &CPEMIs) {
for (MachineFunction::iterator MBBI = Fn.begin(), E = Fn.end();
MBBI != E; ++MBBI) {
MachineBasicBlock &MBB = *MBBI;
@@ -339,9 +378,15 @@
}
// Remember that this is a user of a CP entry.
- MachineInstr *CPEMI =CPEMIs[I->getOperand(op).getConstantPoolIndex()];
+ unsigned CPI = I->getOperand(op).getConstantPoolIndex();
+ MachineInstr *CPEMI = CPEMIs[CPI];
unsigned MaxOffs = ((1 << Bits)-1) * Scale;
CPUsers.push_back(CPUser(I, CPEMI, MaxOffs));
+
+ // Increment corresponding CPEntry reference count.
+ CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
+ assert(CPE && "Cannot find a corresponding CPEntry!");
+ CPE->RefCount++;
// Instructions can only use one CP entry, don't bother scanning the
// rest of the operands.
@@ -415,7 +460,7 @@
// Next, update WaterList. Specifically, we need to add NewMBB as having
// available water after it.
- std::vector<MachineBasicBlock*>::iterator IP =
+ SmallVector<MachineBasicBlock*, 8>::iterator IP =
std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
CompareMBBNumbers);
WaterList.insert(IP, NewBB);
@@ -487,10 +532,9 @@
unsigned AlignAdj = AFI->isThumbFunction() ? 2 : 0;
unsigned CPEOffset = GetOffsetOf(CPEMI) + AlignAdj;
- DEBUG(std::cerr << "User of CPE#" << CPEMI->getOperand(0).getImm()
- << " max delta=" << MaxDisp
- << " at offset " << int(CPEOffset-UserOffset) << "\t"
- << *MI);
+ DOUT << "User of CPE#" << CPEMI->getOperand(0).getImm()
+ << " max delta=" << MaxDisp
+ << " at offset " << int(CPEOffset-UserOffset) << "\t" << *MI;
if (UserOffset <= CPEOffset) {
// User before the CPE.
@@ -504,6 +548,20 @@
return false;
}
+/// BBIsJumpedOver - Return true of the specified basic block's only predecessor
+/// unconditionally branches to its only successor.
+static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
+ if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
+ return false;
+
+ MachineBasicBlock *Succ = *MBB->succ_begin();
+ MachineBasicBlock *Pred = *MBB->pred_begin();
+ MachineInstr *PredMI = &Pred->back();
+ if (PredMI->getOpcode() == ARM::B || PredMI->getOpcode() == ARM::tB)
+ return PredMI->getOperand(0).getMBB() == Succ;
+ return false;
+}
+
/// HandleConstantPoolUser - Analyze the specified user, checking to see if it
/// is out-of-range. If so, pick it up the constant pool value and move it some
/// place in-range.
@@ -550,10 +608,33 @@
unsigned CPI = CPEMI->getOperand(1).getConstantPoolIndex();
unsigned Size = CPEMI->getOperand(2).getImm();
+ // Find the old entry. Eliminate it if it is no longer used.
+ CPEntry *OldCPE = findConstPoolEntry(CPI, CPEMI);
+ assert(OldCPE && "Unexpected!");
+ if (--OldCPE->RefCount == 0) {
+ MachineBasicBlock *OldCPEBB = OldCPE->CPEMI->getParent();
+ if (OldCPEBB->empty()) {
+ // In thumb mode, the size of island is padded by two to compensate for
+ // the alignment requirement.
+ BBSizes[OldCPEBB->getNumber()] = 0;
+ // An island has only one predecessor BB and one successor BB. Check if
+ // this BB's predecessor jumps directly to this BB's successor. This
+ // shouldn't happen currently.
+ assert(!BBIsJumpedOver(OldCPEBB) && "How did this happen?");
+ // FIXME: remove the empty blocks after all the work is done?
+ } else
+ BBSizes[OldCPEBB->getNumber()] -= Size;
+ OldCPE->CPEMI->eraseFromParent();
+ OldCPE->CPEMI = NULL;
+ NumCPEs--;
+ }
+
// Build a new CPE for this user.
U.CPEMI = BuildMI(NewIsland, TII->get(ARM::CONSTPOOL_ENTRY))
.addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
-
+ CPEntries[CPI].push_back(CPEntry(U.CPEMI, CPI, 1));
+ NumCPEs++;
+
// Compensate for .align 2 in thumb mode.
if (isThumb) Size += 2;
// Increase the size of the island block to account for the new entry.
@@ -566,8 +647,7 @@
break;
}
- DEBUG(std::cerr << " Moved CPE to #" << ID << " CPI=" << CPI << "\t"
- << *UserMI);
+ DOUT << " Moved CPE to #" << ID << " CPI=" << CPI << "\t" << *UserMI;
return true;
}
@@ -580,11 +660,10 @@
unsigned BrOffset = GetOffsetOf(MI) + PCAdj;
unsigned DestOffset = GetOffsetOf(DestBB);
- DEBUG(std::cerr << "Branch of destination BB#" << DestBB->getNumber()
- << " from BB#" << MI->getParent()->getNumber()
- << " max delta=" << MaxDisp
- << " at offset " << int(DestOffset-BrOffset) << "\t"
- << *MI);
+ DOUT << "Branch of destination BB#" << DestBB->getNumber()
+ << " from BB#" << MI->getParent()->getNumber()
+ << " max delta=" << MaxDisp
+ << " at offset " << int(DestOffset-BrOffset) << "\t" << *MI;
if (BrOffset <= DestOffset) {
if (DestOffset - BrOffset <= MaxDisp)
@@ -612,7 +691,7 @@
}
/// FixUpUnconditionalBr - Fix up an unconditional branches whose destination is
-/// too far away to fit in its displacement field. If LR register has been
+/// too far away to fit in its displacement field. If LR register ha been
/// spilled in the epilogue, then we can use BL to implement a far jump.
/// Otherwise, add a intermediate branch instruction to to a branch.
bool
@@ -628,7 +707,7 @@
HasFarJump = true;
NumUBrFixed++;
- DEBUG(std::cerr << " Changed B to long jump " << *MI);
+ DOUT << " Changed B to long jump " << *MI;
return true;
}
@@ -677,9 +756,7 @@
// b L1
MachineBasicBlock *NewDest = BMI->getOperand(0).getMachineBasicBlock();
if (BBIsInRange(MI, NewDest, Br.MaxDisp)) {
- DEBUG(std::cerr << " Invert Bcc condition and swap its destination"
- << " with " << *BMI);
-
+ DOUT << " Invert Bcc condition and swap its destination with " << *BMI;
BMI->getOperand(0).setMachineBasicBlock(DestBB);
MI->getOperand(0).setMachineBasicBlock(NewDest);
MI->getOperand(1).setImm(CC);
@@ -696,9 +773,9 @@
}
MachineBasicBlock *NextBB = next(MachineFunction::iterator(MBB));
- DEBUG(std::cerr << " Insert B to BB#" << DestBB->getNumber()
- << " also invert condition and change dest. to BB#"
- << NextBB->getNumber() << "\n");
+ DOUT << " Insert B to BB#" << DestBB->getNumber()
+ << " also invert condition and change dest. to BB#"
+ << NextBB->getNumber() << "\n";
// Insert a unconditional branch and replace the conditional branch.
// Also update the ImmBranch as well as adding a new entry for the new branch.
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